---

{}

---

Surgical Site Infection (SSI)

Introduction

• Second most common cause of hospital-acquired infections (HAIs), following urinary tract infections (UTIs).
• Consequences:
  • Prolonged hospital stays, significantly increased healthcare costs, and higher mortality rates in certain types of surgery.
  • Five-fold increase in hospital readmissions, 60% more likely to be admitted to ICU, and twice as likely to die.

Definition

• Infections occurring within 30 days post-surgery with no implant or within 1 year if an implant is placed and the infection appears related to the surgery.
• Classified as incisional (superficial vs. deep) or organ/space infections.

Risk Factors for Development of Postoperative Surgical Infection

Patient Factors

• Diabetes mellitus
• Obesity
• Smoking
• Bacterial colonization
• Remote infection
• Older age
• Underlying illness
• Malnutrition
• Hypoxemia
• Surgical technique
• Site and type of surgery
• Length of procedure

Perioperative Variables

• Operating theatre characteristics
• Use of foreign materials
• Antibiotic prophylaxis
• Hand hygiene
• Invasive anesthetic procedures
• Hypothermia
• Face masks and theatre traffic
• Regional anesthesia
• Tissue oxygenation
• Perioperative glycaemic control
• Volume status and fluid replacement
• Transfusion of allogeneic blood products
• Postoperative pain control

Principles of Surveillance

• Chart review
• Medication review
• Laboratory-based ward surveillance
• Laboratory-based telephone surveillance
• Ward liaison surveillance
• Treatment and temperature chart surveillance
• Risk factor surveillance
• Antimicrobial use monitoring
• Microbiology reports

Principles of an Effective Surveillance System

• Maintain accurate, efficient, and confidential data collection.
• Provide data on final infection rates stratified by multivariate risk for each surgeon and patient.
• Use clear, consistent definitions of infection.
• Use standardized post-discharge follow-up protocols and proper maintenance of data.

Surgical Wound Classification

• Clean Surgery: No break in aseptic technique; respiratory, gastrointestinal, or genitourinary tracts are not breached.
• Clean-Contaminated Surgery: Includes operations on the oropharynx, sterile genitourinary or biliary tract, gastrointestinal or respiratory tracts, or minor breaches in aseptic technique.
• Contaminated Surgery: Presence of acute inflammation, infected bilious secretions, infected urine, or gross contamination from the gastrointestinal tract.
• Dirty Surgery: Established infection exists, and therapeutic antibiotics are administered based on susceptibility of bacterial isolates from culture.

Pre-Operative, Peri-Operative, and Antibiotic Protocols

Pre-Operative

• Full body wash
• Prepare surgical site immediately before incision
• Decontaminate hands
• Remove hair on table (preferably with electric clippers)

Peri-Operative

• Maintain oxygen saturation >95%
• Monitor and correct blood glucose
• Maintain normothermia

Antibiotics

• Use prophylactically for clean-contaminated, contaminated, or dirty surgery.
• Select antibiotics according to guidelines based on the operation and local resistance patterns.
• Administer IV within 60 minutes before incision.
• Repeat dose if operation exceeds the antibiotic’s half-life.
• Do not routinely continue antibiotics beyond 24 hours.

Modifiable Factors by Anaesthetist to Prevent SSI

• Hand hygiene
• Minimize theatre traffic
• Antibiotic prophylaxis
• Perform invasive procedures aseptically
• Prevent hypothermia
• Use regional anesthesia where possible
• Ensure tissue oxygenation
• Control blood glucose
• Limit blood transfusions
• Postoperative pain control

Interventions to Prevent SSI

Pre-Operative

• Shower with plain soap
• 2% mupirocin for nasal carriers of Staphylococcus aureus (cardiac and orthopedic surgery)
• Avoid hair removal or use clippers if necessary
• Administer antibiotics within 120 minutes before incision
• Scrub with antimicrobial soap or alcohol-based hand rub
• Mechanical bowel preparation with antibiotics (for colorectal surgery)
• Nutritional optimization (especially for underweight patients)
• Continue immunosuppressants as indicated
• Ensure clean instruments and theatre environment

Intra-Operative

• Avoid laminar airflow ventilation
• Avoid plastic adhesive drapes
• Use alcohol-based skin prep without antimicrobial skin sealants
• Maintain 80% oxygen concentration
• Ensure normothermia
• Control glucose levels with a protocol
• Implement goal-directed fluid therapy
• Use aqueous povidone over wound (clean or clean-contaminated)
• Employ wound protectors (except in clean wounds)
• Apply negative pressure wound therapy for high-risk wounds
• Use triclosan-coated sutures
• Maintain theatre asepsis

Post-Operative

• Maintain 80% FiO2 for 2-6 hours
• Avoid prolonged antibiotic prophylaxis
• Ensure good wound care

Surgical Prophylaxis

Operation	Prophylaxis recommendation	Recommended agent	Alternative for beta-lactam allergy
Neurosurgery
Craniotomy	Recommended	Cefazolin	Clindamycin, vancomycin
Spinal surgery	Recommended	Cefazolin	Clindamycin, vancomycin
Head and Neck Surgery
Clean head/neck ORIF	Recommended	Cefazolin + metronidazole or amoxicillin/clavulanate	Replace cefazolin with clindamycin
Clean head/neck dissection	Recommended	Cefazolin	Clindamycin, vancomycin
Ear surgery (no prosthesis)	Not recommended	–	–
Ear surgery with prosthesis	Recommended	Cefazolin	Clindamycin, vancomycin
Dental Surgery
No implant involved–benign	Not recommended	–	–
Extraction and implant	Should be considered	Amoxicillin/clavulanate	Clindamycin
Upper GI Surgery
Esophageal surgery	Recommended	Cefazolin	Clindamycin, vancomycin
Gastroduodenal surgery	Recommended	Cefazolin	Clindamycin, vancomycin
Hepatobiliary Surgery
Bile duct surgery	Recommended	Cefazolin + metronidazole or cefoxitin	Clindamycin + gentamicin
Pancreas surgery	Recommended	Cefazolin + metronidazole or cefoxitin	Clindamycin + gentamicin
Lower GI Surgery
Appendectomy	Recommended	Cefazolin + metronidazole or cefoxitin	Clindamycin + gentamicin
Colorectal surgery	Recommended	Cefazolin + metronidazole or cefoxitin	Clindamycin + gentamicin
Obstetrics and Gynecology
Hysterectomy	Recommended	Cefazolin + metronidazole or cefoxitin	Clindamycin + gentamicin
Termination of pregnancy	Not recommended	–	–
Urology
Cystoscopy (sterile urine)	Not recommended	–	–
Transurethral resection of prostate/bladder tumor	Recommended	Ciprofloxacin	Gentamicin
Cystectomy	Recommended	Cefazolin + metronidazole or cefoxitin	Clindamycin + gentamicin
Orthopedic Surgery
Clean orthopedic surgery without prosthesis	Recommended	Cefazolin	Clindamycin, vancomycin
Clean orthopedic surgery with prosthesis	Recommended	Cefazolin	Clindamycin, vancomycin
Vascular Surgery
Aortic surgery	Recommended	Cefazolin	Clindamycin, vancomycin
Lower limb amputation	Recommended	Cefazolin + metronidazole or cefoxitin	Clindamycin + gentamicin

Agent Choice

• The agent should target pathogens most likely to contaminate the wound, be administered in doses adequate to maintain tissue levels for the potential contamination period, and be continued for the shortest effective duration.
• Prefer antibiotics with a narrow spectrum to minimize the risk of antibiotic resistance. Avoid using antibiotics typically used for treating infections.
• Cefazolin: Commonly used for prophylaxis in most surgical procedures.
  • Narrow spectrum, active against staphylococci, some Gram-negatives, and other bacteria likely to contaminate the operative site.
  • Duration of action is sufficient for most procedures.
  • Safe and cost-effective.

Microflora of Different Anatomical Sites

• Skin: Staphylococcus aureus or coagulase-negative staphylococci
• Cardiac: Gram-positives including S. aureus and coagulase-negative staphylococci
• Thoracic: Predominantly Gram-positives
• Gastroduodenal: Coliforms (Escherichia coli, Proteus species, Klebsiella species), Gram-positives (staphylococci, streptococci, enterococci)
• Biliary Tract: Gram-negatives and Gram-positives (E. coli, Klebsiella species, enterococci, streptococci, staphylococci)
• Small Intestine: Predominantly Gram-negatives
• Colorectal: Anaerobes (Bacteroides fragilis) and Enterobacteriaceae (E. coli)
• Head and Neck: S. aureus, streptococci (aerobic and anaerobic), other anaerobes
• Neurosurgery: Gram-positives (S. aureus and coagulase-negative staphylococci)
• Gynaecological: Gram-positives, Gram-negatives, and anaerobes
• Urological: E. coli and other Gram-negatives

Specific Operations and Agents

• Prophylaxis Regimens for Commonly Performed Procedures
  • Clean-contaminated and contaminated wounds.
  • Use of antibiotics in the presence of a dirty wound is considered treatment of an established infection.
  • Indicated when prosthesis is used.
  • Patient-related factors:
    • Poor nutritional status, obesity, diabetes, smoking, extremes of age, immune system compromise (e.g., corticosteroid therapy, HIV, chemotherapy, systemic illness), long hospital stays before the procedure, colonization with specific bacterial strains.

Adverse Effects

• Drug allergy, anaphylaxis, antibiotic-associated diarrhea, Clostridium difficile infection, antibiotic resistance.

Special Patient Populations

• Colonized or Recently Infected with Multi-Drug Resistant Pathogens:
  • Unique considerations for extending antibiotic cover based on the antibiotic sensitivity of the bacteria and the proximity of the probable colonization site to the surgical site.
  • MRSA: Extend prophylaxis to cover MRSA; vancomycin reserved for these cases.
• Receiving Antibiotics for an Infection at a Different Site:
  • Modify SAP if current antibiotics cover expected pathogens at the surgical site. Administer an extra dose within 60 minutes of incision if covered; otherwise, use recommended prophylaxis independently.
• Pregnancy:
  • Robust meta-analyses show that pre-incision administration of prophylactic antibiotics significantly reduces maternal infectious morbidity without adverse neonatal outcomes.

Timing

• Administer antibiotics within 60 minutes of skin incision to reduce SSI rates.
  • Fluoroquinolones and glycopeptides (e.g., vancomycin) should start 120 minutes before skin incision due to infusion requirements.

Dose

• Use standardized doses for adults; adjust for obesity to ensure optimal tissue concentrations.
  • Cefazolin: 1 g for adults <80 kg, 2 g for adults >80 kg, and 3 g for adults >120 kg.
  • Gentamicin: Use ideal body weight plus 40% of the difference between total and ideal body weight.
  • Insufficient evidence for other antibiotics in obesity.
• Single preoperative doses do not require modification for renal or liver dysfunction.

Redosing

• Redose if the procedure duration exceeds two half-lives of the drug or in cases of >1,500 ml blood loss.
• Patients with renal dysfunction may require longer intervals till redosing.

Antibiotic	Adult Dose	Pediatric Dose	Redosing Interval (hours)
Amoxicillin/clavulanate	1.2 g	30 mg/kg of amoxicillin component	4
Cefoxitin	2 g	40 mg/kg	2
Cefazolin	2 g ≥ 80 kg, 3 g ≥ 120 kg	25–30 mg/kg	4
Ciprofloxacin	400 mg	10 mg/kg	NA*
Clindamycin	900 mg ≥ 70 kg, 600 mg < 70 kg	10 mg/kg	NA*
Fluconazole	400 mg	6 mg/kg	6
Gentamicin	5 mg/kg	2.5–5 mg/kg	NA*
Levofloxacin	500 mg	15 mg/kg	NA*
Metronidazole	500 mg–1 g	15 mg/kg	NA*
Piperacillin-tazobactam	4.5 g	Infants 2–9 mo: 80 mg/kg of piperacillin component Children > 9 mo: 100 mg/kg of piperacillin component	2
Vancomycin	15 mg/kg	15 mg/kg	NA*

*NA–Not applicable due to prolonged half-life of the drug

Duration of Prophylaxis

• Prophylaxis for the duration of the procedure is sufficient; longer durations provide no added benefit.
  • Controversial practice in cardiothoracic procedures; some guidelines allow up to 24-48 hours.
• For hip and knee arthroplasty, continuing prophylaxis for 24 hours postoperatively is considered the gold standard but lacks supporting evidence. Further large, multicenter RCTs are recommended.

Links

• Infection control
• Infection and antibiotics
• Pre-op assessment and investigation
• Premedication
• Infective endocarditis

---

---

References:

1. Surgical antibiotic prophylaxis: Are you doing it right? J Jocum. WITS refresher 2018

Summaries:

---

—
Copyright
© 2022 Francois Uys. All Rights Reserved.